Millions of gallons of paint are sprayed every year worldwide, thereby generating airborne pollution from the paint overspray. Outdoor spray painting of large structures (e.g. bridges, water towers, railroad cars, buildings, and ships) faces stringent discharge regulations limiting the emission of airborne pollutants. Failure to meet such discharge regulations can lead to notices of violation, fines, negative publicity, increased operating costs and delays in work completion. Also, overspray from spray painting often contains toxic particulates and volatile organic compounds which are very difficult to prevent from dispersing into the atmosphere.
In fluid dynamic terms, the three categories of spray painting are airblast atomization, pressure atomization, or some combination of the two. The first category is termed "conventional airspray" in the industry, while the second is known as "airless" paint spraying. Hybrid approaches make up the third category. Transfer efficiency for spray painting is known as the percentage of the total paint sprayed which eventually adheres to the work surface. The paint which does not adhere to the work surface and escapes to the environment is the overspray. Conventional airspray has a transfer efficiency typically in the range of only 20-30%, which has become environmentally unacceptable. Airless spray, on the other hand, has a transfer efficiency often above 50% or better, but with considerable room for improvement. Professional spray-painting equipment is classified by the method of paint atomization (e.g. airspray, airless, air-assisted airless, etc.). In essentially all cases, the spray from a spray gun is shaped in the form of an elongated spray ellipse or "fan" to ease the application of a uniform coating. Whether hand-held or manipulated robotically, the spray gun is traversed in the direction of the short axis of this ellipse, while held perpendicular to the work surface at a fixed spraying distance usually of about twelve (12) inches.
Current industrial spray painting practice involves the use of large temporary containment enclosures to prevent the escape of overspray. These temporary containment enclosures are usually clumsy and ineffective, as they take a brute-force approach rather than invoking aerodynamics of the process to capture the overspray near its source. Such containment enclosures are also labor-intensive to use, have questionable effectiveness and are very costly. No real solution has been presented for painting large outdoor structures or objects. Most of the prior art deals with overspray during the coating of small to moderate-sized indoor objects which are enclosed in a spray booth. An improved technical solution to the problem of spray painting large outdoor objects or structures is seriously needed to meet today's overspray containment standards.
An object of the present invention is to provide an apparatus and method to manage and capture overspray from a spraying device during coating operations of a surface.
Another object of the present invention is to provide an apparatus and method for capturing overspray while coating large outdoor surfaces and structures.
Another object of the present invention is to provide an apparatus for capturing overspray, whereby the apparatus moves with the spraying device during the coating process.